1. Field of the Invention
The present invention relates to a power capping apparatus and method.
2. Discussion of Related Art
Conventional power capping technology is technology of limiting a used amount of power used in a computing system with a capping value set by a system administrator, and is technology used when power supply is insufficient in a server system of a data center or for operating the system within a predetermined amount of power. There are methods of limiting a total used amount of power in a power supply unit installed in the computing system, and of limiting a used amount of power of various devices (a central processing unit (CPU), a memory, an input/output (I/O) device, etc.) included in the computing system, in the power capping technology.
As shown in FIG. 1, a basic conventional power capping method measures a total used amount of power used by the computing system, and limits a used amount of power of components capable of controlling the used amount of power or a total system when the used amount of power is greater than a power limit value (a capping value) set by a user. FIG. 1 is a drawing illustrating a conventional power capping method.
The computing system to which conventional power capping technology is applied has disadvantages in which degradation of performance is accompanied and a processing time of a job is delayed while executing, since the used amount of power is decreased when a power limiting function is driven. That is, in the conventional power capping methods, the delay of the processing time of the job is not considered due to the degradation of performance accompanied due to the power limitation. Energy (E) with respect to power (P) and a time (T) is represented by the following Equation 1, and the energy E may be equal to an amount of the job performed.E=P×T  [Equation 1]
That is, it may be regarded as the same amount of the job when a decrease of the used amount of power and a time are increased at the same ratio. For example, when using the conventional power capping method, as shown in a left side of FIG. 2, a job of E1 in which a time t1 is taken using the used amount of power P1 not using a power capping function has to be performed as E2 which is the same amount of the job as E1 even when a time t2 is taken when setting as the used amount of power P2 using the power capping function. However, as shown in a right side of FIG. 2, the delay of the processing time is increased more than a ratio in which the used amount of power is decreased and thus a state of E1<E2′ occurs. In a standpoint of energy, an energy saving effect is represented as follows according to states of E1 and E2′.
E1<E2′: no energy saving effect
E1=E2′: the same consumed amount of energy
E1>E2′: energy saving effect
As such, the conventional power capping method does not consider the degradation of performance of the system, and limits the used amount of power of the system. Accordingly, in the standpoint of energy, the conventional power capping method has a problem in that more energy is consumed, and a processing amount of the job capable of being completed within a predetermined time is decreased according to the limitation of the used amount of power.